1. Field of the Invention
The invention relates to communications systems in general and, more specifically, the invention relates to a video compression technique suitable for use in an interactive multimedia information delivery system.
2. Description of the Background Art
Over the past few years, the television industry has seen a transformation in a variety of techniques by which its programming is distributed to consumers. Cable television systems are doubling or even tripling system bandwidth with the migration to hybrid fiber coax (HFC) cable transmission systems. Customers unwilling to subscribe to local cable systems have switched, in high numbers to direct broadcast satellite (DBS) systems. And, a variety of other approaches have been attempted focusing primarily on high bandwidth digital technologies, intelligent two way set top boxes, or other methods of attempting to offer service differentiated from standard cable and over the air broadcast systems.
With this increase in bandwidth, the number of programming choices has also increased. Leveraging off the availability of more intelligent set top boxes, several companies have developed elaborate systems for providing an interactive listing of a vast array of channel offerings, expanded textual information about individual programs, the ability to look forward to plan television viewing as much as several weeks in advance, and the option of automatically programming a video cassette recorder (VCR) to record a future broadcast of a television program.
Unfortunately, the existing program guides have several drawbacks. They tend to require a significant amount of memory, some of them needing upwards of one megabyte of memory at the set top terminal (STT). They are very slow to acquire their current database of programming information when they are turned on for the first time or are subsequently restarted (e.g., a large database may be downloaded to a STT using only a vertical blanking interval (VBI) data insertion technique). Disadvantageously, such slow database acquisition may result in out-of-date database information or, in the case of a pay-per-view (PPV) or video-on-demand (VOD) system, limited scheduling flexibility for the information provider.
Therefore, it is desirable to provide a data compression and decompression technique that enables interactive program guides having graphics and video portions to be efficiently transmitted through an interactive information distribution system.
The invention is a method and apparatus for compressing and transmitting both video and graphics portions of an interactive program guide (IPG). For an IPG that comprises a graphics portion and one or more video portions, the inventive system separately encodes the video portion and the graphics portion. The video portion is slice-base encoded using a predictive encoder, e.g., an MPEG encoder, that produces a bitstream comprising intra-coded picture slices and predictive-coded picture slices. The graphics portion is separately slice-base encoded to produce encoded slices of the graphics image. The encoded slices of the graphics portion can be stored in a database and recalled as needed for transmission. To transmit an IPG, a transport stream is created containing the intra-coded and predictive-coded video streams as well as the encoded slices that comprise a graphics image that is to be included in the IPG. The receiver reassembles the components of the IPG by decoding the slice-based streams.